Here’s a quick update on what technology the EV companies are using for cabin heating:

The Tesla Model S does not have a heat pump but uses waste heat recovery from the drive unit and power electronics to heat its battery-in addition to an electric battery and cabin heater. Nissan Leaf uses a simple (not injected) heat pump. GM Volt and Spark EV use resistive heating. As to future models, we don’t know what Tesla will use in the Model 3 or what GM will use in Bolt EV. Tesla hinted at some new HVAC tech during the Model 3 unveiling.

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How does Vapor Injection work?

Please note that the following technical description is not from Toyota but from one of the authors who is licensed HVAC engineer with over 35 years of experience in heating ventilation and air conditioning systems.

Have you ever heard of inter-cooling? This new heat pump tech works in much the same way by cooling the refrigerant during the compression process.

Inter-cooling is not new technology and has been used in industrial refrigeration systems by using two stages of compression with cooling in between the stages…..an expensive way to implement because you need a two stage compressor and an intercooler.

Recent simplifications have lowered the cost however. We now can accomplish the same effect at a lower cost just by injecting a small amount of cold refrigerant vapor into the compressor during the compression process. We simply tap off a small amount of cold vapor and inject it into the compressor.

Looks simple right? Well, not quite, as we need to separate some liquid particles out of the cold vapor before we inject the cold vapor into the compressor. There are two ways to separate the liquid. The lowest cost method is with liquid sub cooling which is shown in the detailed engineering schematic figure 2. Emerson has chosen this approach. A typical 2.5 ton automotive heat pump set up for vapor injection would have approximately $300 in additional parts: one new modulating expansion valve, one sub cooling heat exchanger, a solenoid valve, tubing, plus the special modifications to the compressor, plus some additional controls.

Stepping back, one has to ask: Why is Toyota going to all this additional complexity for a low AER plug in vehicle that has a gasoline engine? There’s plenty of waste heat available from the engine. This complex of a system would be better suited for a pure BEV in our opinion. Perhaps Toyota DOES have a secret BEV project waiting in the wings and the Mirai is just a ruse!

Given that this system would be better suited for a pure BEV, do you think this would be a worthwhile option for the Tesla model 3 or Bolt EV?

— or does Tesla have a better way by simply using waste heat to warm things up?

About the authors:George Bower is a retired mechanical engineer with over 20 years experience in gas turbine power systems.

Keith Ritter is a mechanical engineer, and licensed professional engineer with over 35 years of experience in heating ventilation and air conditioning systems.

Tesla won’t use a heat pump, because it most certainly means loosing the frunk, a distinctive and highly sought feature.

If Elon can get people that can land a 12-story rocket on a tiny drone ship in the middle of the ocean AFTER it’s delivered payload to orbit, he can get some who can figure out how to efficiently heat a car in the winter.

If they put a proper trunk in the car, he would not need the ridiculous frunk …. but yes, let’s rather have a frunk and 100’s of rocket ship engineers to invent a heating device which consumes very low amount of energy.

The S and X trunks are no different than any other available trunks. The frunks exist because the design choice was to make the EV look “normal”, even though there is no engine to fill that space. So, it’s extra storage.

The mainstream market, including me, is not ready for a jelly bean (I really don’t like the looks of the i-MiEV).

I dig the frunk. Not only is it valuable as extra storage space when that’s needed, but it’s the perfect place for everyday use. I don’t haul around luggage or other big items very often, but I shop groceries three or more times a week. It’s great to put them in a room where they don’t fly about as freely.

There is little correlation between frunk space and heat pump space requirements. From a space standpoint, Tesla could easily fit Model S with a “conventional” heat pump with no impact on frunk space. The Model S already has an AC compressor and the related coils and valves. A conventional heat pump system is the same size as an AC system with largely the same components. For this advanced heat pump, the only additional component taking up substantive space is the sub-cooling heat exchanger. One additional component might reduce frunk space some, but not kill it.

Question to Elon Musk: how about using extra battery pack, like those recently advertised as a kind of “jerry can” for electric cars. Of course some extra connectors are needed somewhere in the trunk. This would help with so called range enxiety.

Not sure about this heat pump, but it sure seems like it has potential. If so, and really works and is a reasonable cost, it could alleviate much of not all of the complaints we northern BEV drivers have in the winter.

There’s a sweet spot, where this is most useful. As electric range grows, the one-time call for cabin heating takes a smaller percentage of those range miles away. Peoaple don’t care. So, I wouldn’t agree a long-range BEV is where it makes the most sense, over one with shorter range or even a PHEV.

Much like GM appears to pursue more of a PHEV/EREV strategy, Toyota may try the same. It’s a ticket out of DCFC sponsorship. The frustration that already shows in focus groups, is the impact on the winter range of smaller batteries. Though I never found out the marques behind it, I was in such a focus group two years ago.

I care. With northern winter range loses in the 40 to 50%, this impacts long distance trips. But for local commuting and errands it’s not as much of a factor.
However, wouldn’t it be nice if a 200 mile range car always was close to that capability regardless of the outside temp.

Heating is not a one-time call. It is needed continuously to keep the cabin warm, although heating power is less than initial heating burst.

Moreover, long range BEV is often used for shorter distances with breaks in between. You may need that heating burst several times before next opportunity to charge. Think about going for business visits to several customer locations within a working day. Each visit maybe 1-2 hours, which is enough to make the car freezing cold.

It makes sense, but what about long wait in traffic jam?
Or being stuck in a snowstorm?
I do think any affordable tech that improves efficiency is worth of using.
That system would double the range of my Leaf MY 12 in winter, although even the MY13 and more recent do improve a lot with their normal heat pump.

I’m positive they are working on one. I think they have seen the writing on the wall. The thing is, they may be a year or two away from being able to produce it. In the meantime, they might as well pretend they don’t believe in EVs and try to sell you a hybrid. It doesn’t really help their business to promote a vehicle they don’t have yet.

Yeah, the massive Japanese oil industry that is overwhelming the world with cheap oil and LNG, driving both US shale and the Sauds out of business. Japan is importing oil/NG like crazy, especially with the nuke plant shutdowns. If you know anything about WWII, you’d know that a big factor motivating Japan was to secure petroleum resources in areas like Indonesia, as Japan was essentially oil-less.

Both Heat Pump and additional heating elements have a place. While heat pumps can no go down to 5 degrees fahrenheit (2 Celsius), On those really cold days (-10 below) Having extra heating elements helps. While heat pumps work,at extreme temperatures they are running all the time and not the most silent.

A heat pump that extracts heat from air will start needing defrosting at 0oC 32 farenheit. At a certain point (around – 8oC) the defrosting electricity exceeds the heat output from the heat pump and it will be more efficient to heat the cabin with electricity directly

Note that it’s a big deal to maintain range: do that and you don’t need as much battery and it could make the difference between running the engine and not running the engine. Every cold start avoided is a very good thing.

Well huge Emerson has now purchased Vilter, the long time well respected refrigeration recipricating and screw chiller manufacturer who has done much pioneering work with this ‘simplified’ intercooling method.

If the system is reliable and doesn’t add too much complication, why not?

The new Prius will certainly be a good test of the cost-effectiveness of this system and its reliability, but then Emerson through their Vilter acquisition no doubt has many hours of real world experience here (with their screw compressors) – so its not a super big surprise that Toyota would try the system out in a heat pump for a car.

Again, if it ultimately is not too much money, and the effect is good, why not? If it ultimately proves too little benefit for too much money and complication, they can always ask Mitsubishi to put one of their hyper-heat pumps in their cars. Now those things really do work in the cold.

(On a side note thermoacoustic has the extra interest of being one of the 3 Venus top of Maxwell Montes settling enabling technologies, the other two being Hydreliox breathing gas at 45 bar and glass foam insulation materials.)

The KIA SOUL EV has the most efficient heat pump of any car. It would be good to have an outside testing group compare the heat pumps and show the results. I bet it just a few % at most.
Now an old compressor air cond is 3 to 4 times more wasteful so that shows why Heat Pumps are so common on efficient vehicles.

Model S uses (blows with fans?) waste heat and electrical (resistive) heating elements. So it seems to me the smarter change, if any, would be to replace the resistive elements with pumped heat, not to stop using waste heat.

Though for all I know it may be that a heat pump is more efficient than moving (fans? radiators??) waste heat, in which case having only pumps might be preferable.

Why don’t Gm reuse the heater designed and produced for the elctric Chevy S-10? I have the Owner Manual, and it described a Diesel fueled heater that is located near the power steering in the front bay (or motor bay since there is no “engine”).

“Why is Toyota going to all this additional complexity for a low AER plug in vehicle that has a gasoline engine? There’s plenty of waste heat available from the engine.”

There is NOT always plenty of waste heat from the gasoline engine.

Neither the plug-in, nor the non plug-in Prius have enough waste heat to heat the cabin to a comfortable temperature within an acceptable amount of time during cold weather and city traffic.

That is why the Prius climate control systems were programmed to turn on the gasoline engine for the sole purpose of heating the interior under such conditions. And many Prii delivered to northern countries came with additional electric resistance heaters built in to the HVAC unit as standard equipment.

For more range and/or efficiency in cold weather it’s a tradeoff: more batteries, or a more complex heating system.

I think it’s apparent that there is not much room left in the Prius Prime for more batteries. For other EVs and Plug-ins it may be more practical to add more batteries.

Heat pump systems might also appear in non plug-in cars in the future. Aside from the emissions and efficiency benefits, they might me marketed as a comfort feature, providing nearly instant heat at startup.